This invention relates generally to electrical generator control systems and more particularly, to selectable frequency, voltage, protection and output ratings for electrical generators.
Engine generator sets are commonly utilized as prime or backup power sources for electrically driven equipment in applications and locations having different power supply requirements. For example, many locales require a 50 Hertz (Hz) electrical output, while others require a 60 Hz output, to match the operating frequency of the local grid. Engine generator set applications may have different power requirements. Voltage and frequency requirements of equipment powered by the engine generator set may vary. For example, in the United States 480V and 60 Hz is a common requirement for electrical equipment, whereas European applications are more likely to need 400V and 50 Hz power. Engine generator sets that are able to provide a certain power level at one voltage and frequency may not be able to supply the same power at another voltage and frequency.
Known engine generator sets are configured to accommodate operation in areas that include electrical systems having 50 Hz or 60 Hz. If an engine generator set is moved from one area to another having a different operating frequency, modifications to settings of generator protection devices, to electrically-powered auxiliary equipment, and to mechanical components are typically required.
Typically, engine generator set auxiliary equipment is powered from the output of the engine generator set. Accordingly, electrical equipment such as pump motors operate at the frequency that the engine generator set is designed to operate. Furthermore, mechanical components coupled to electric motors are sized to accommodate the output power levels of the electric motors to which the mechanical component is coupled.
Voltage regulators are typically designed to operate with a variety of different engine generator sets with a wide range of capabilities. Thus, a particular engine generator set, may not be capable of operating at all voltage choices available on the voltage regulator. The engine generator set also may not be able to meet the same power rating at one voltage as it can at a different voltage. In addition to setting the engine and voltage ratings for a particular application, relays and other protective devices contained in the engine generator set control system will need to be reset or replaced when the operation of the engine generator set is to be changed from one frequency to another. Protective relaying, such as over and under voltage relays and over and under frequency relays, disconnects a load, shuts down the engine, prevents excitation of the generator or protects the engine generator set in some other manner if a condition that could cause damage to the engine generator set is detected. For example, if the voltage exceeds the acceptable rating and the engine generator set has an overvoltage relay, the relay may trip a circuit breaker and disconnect the load, thus preventing damage to both the generator and the load. Relays must be set correctly to operate. For example, the voltage level at which the overvoltage relay will trip a circuit breaker is typically set manually.
To change the operation of an engine generator set from one operating frequency to a different frequency, a user may need a variety of skills. The user may need to change the engine rating, to change the voltage and frequency on the voltage regulator manually, to set protective relays, and to replace motors, pumps, heaters and other auxiliary equipment, and to ensure all settings and ratings are compatible with each other and the engine generator set. Technicians with these skills may be difficult to find in the remote areas where engine generator sets often run. The amount of labor and the cost of parts required may reduce the feasibility of a particular application, and the more steps the technician has to take to setup a engine generator set, the more chances there are for error.